Pigeon Fever!

Spreading across America, Pigeon Fever is becoming an increasingly common disease to horses. The earliest recognition of it was in 1915, in California. Slowly it has been stretching to parts of the Southwest. Pigeon Fever is caused by the bacteria Cornyebacterium pseudotuberculosis which is mostly found in soil that is dry and mixed with manure. It can enter the horses’ body through open wounds, penetrating through the skin or other physical contact. Flies may also be carriers of the bacteria and transmit it to a horse when they bite them. When the pathogen gains access to the body it begins to multiply, triggering the immune system to produce white blood cells called macrophages that absorb and destroy invaders. There are two qualities of C. pseudotuberculosis that allows it to protect itself against the macrophages. The first it its waxy lipid outer covering that defies the macrophages effort to destroy it. Another is its ability to release the toxin, phospholipase D, which degrades cell membranes. This causes leakage and cell death of the endothelial cells that line the blood and lymph vessels and causes swelling. This will lead the body to respond in force by constructing a thick walled abscess around the site of leakage. There are three types of abscesses that Pigeon Fever can cause. One is external abscesses that are located under the skin or in the musculature. The second is an internal abscess that will occur in the liver, lungs, kidneys, or other organs. Lastly, an ulcerative lymphangitis can occur and will affect the lymphatic system in the lower leg. Some ways to tell if your horse has Pigeon Fever is any hard swellings, a fever, or any soreness or lameness.

From magazine Equus, article: On the Watch for Pigeon Fever
by: Heather Smith Thomas with Laurie Bonner